Charlbury has beaten previous standing British heat record

Fri 22 Jul 2022, 19:27 (last edited on Fri 22 Jul 2022, 19:28)

Where does John keep his anenometer? Pole? Roof ridge? Always find the windspeed indicators don't reflect Hundley Way, or indeed our garden. Despite being pretty well bang on the levelling out of the slope - although The Green does rise a few metres more, quite sharple, heading east - we are probably quite well sheltered. Wonder whether an anenometer up 16 foot on the TV  mast above the ridge is a valid spot? Though I am not going up a ladder to bolt it on!

Fri 22 Jul 2022, 09:36

I have found another Charlbury weather station at Hill Close where the data is available on-line. That's because it uploads data to a public Met Office database for private weather stations.


This is the chart of the temperature from Hill Close, where, looking at the detailed date, the highest temperature…

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Thu 21 Jul 2022, 14:51

Given the altitude distance, our western end of The Green being at the peak - neearly - of the ridge in the long climb up from the Rosie, wind effects and other microclimate variables that might have an effect ... maybe I should treat myself to a nice little no-frills internet connected weatherstaion of my very own, but to share too. Then when we go out with the dogs and find John's recorded windspeed down in sheltered Paddock land bears no relation to the actual bluster of t'Way, will be pre-warned.

Thu 21 Jul 2022, 14:18

Yes. I am sure it is altitude that matters more than distance. And it is in winter that the Charlbury and Charlbury YHA forecasts most often diverge.

And so they should, given that snow and ice linger much longer up on the hill than in the town itself.

Of course when you are at home, the forecast is these days tailored to your home address. But the YHA option is useful when looking remotely or when you have location turned off as an option. 

Thu 21 Jul 2022, 11:39 (last edited on Thu 21 Jul 2022, 11:42)

It is, indeed, the grid reference that matters for the weather forecast and not the nearest weather station. The latter is just referenced as there is 24 hours of past data available.

If you search for forecasts, then the Met Office site knows about "Charlbury Youth Hostel", but then it also knows about Charlbury too and it appears the actual forecast is identical (no surprise).

If I look for "Charlbury Met Office last 24 hours", then it shows Brize Norton as the closest weather station (9.0 miles) whilst Charlbury Youth Hostel last 24 hours gives the Little Rissington weather station as the closest (9.6 miles). This raised some questions with me.

A bit of geometry, and looking up the coordinates for the Little Rissington and Brize Norton weather stations (51.8667 N, 1.6833 W and 51.75 N, 1.5833 W respectively), and the co-ordinates for the old YHA of the Slade (51.8756 N, 1.4770 W), I get 9.8 miles to Brize Norton and 8.8 miles to Little Rissington. For Brize Norton to be closer, than Little Rissington, you have to locate the centre somewhere like Finstock and not the centre of Charlbury (Little Rissington is still about 0.7 miles closer to Bull Corner than Brize Norton). Note these are the actual weather station co-ordinates, not that of the places they take their name from.

So, maybe it's not simple distance that's used by the Met Office to locate the nearest weather station. Possibly they factor in altitude too. It's not enough to substantially affect the actual linear distance, but maybe altitude is more important for comparable weather, and the old YHA is significantly higher than the centre of town.

nb. not, coincidentally, both Little Rissington and Brize Norton weather stations are located on RAF stations.

Thu 21 Jul 2022, 08:35

The weather data locations referred to reflect the differing availability of  forecast and actual measured data. Forecast values will be taken from a grid point (of which there are many millions) in the numerical forecast model nearest to the chosen location. Actual readings are limited by what is available and are much fewer. I assume that height amsl as well as distance means that Little Rissington is considered more representative for the ‘Youth Hostel’ and Brize Norton more relevant to those of us in the lower parts of town. This is probably a moot point however as Brize Norton location and exposure is somewhat different to all of us.

Wed 20 Jul 2022, 23:12 (last edited on Wed 20 Jul 2022, 23:12)

Yes, Malcolm, it closed in 2001. But if you use the Met Office app and website , it gives a different forecast for Charlbury and Charlbury YHA, ie the top of The Slade. And I always prefer the YHA one as it more closely matches the weather at my house. Often significantly different.

Steve has now helpfully explained that the readings for the YHA building (which is of course still there) are actually derived from Little Rissington, rather than from Brize Norton which gives the forecast for central Charlbury. 

Wed 20 Jul 2022, 22:35

I'm baffled by references to Charlbury Youth Hostel! I thought it had closed down years - decades - ago as we live about 150 yards as the crow etc away from where it was supposed to be. Where are the readings being taken from, then?

Wed 20 Jul 2022, 18:14 (last edited on Wed 20 Jul 2022, 18:21)

I cannot find any on-line weather measurements for Charlbury YHA. Forecasts, yes, but no measurements. If they are available, then they'd clearly be very representative, and not too far from me. As it is, then if I search I do get this hit :-

Click through and it gives you…

Long post - click to read full text

Wed 20 Jul 2022, 16:35 (last edited on Wed 20 Jul 2022, 16:55)

I recorded the temperature on Tuesday in my sunny back garden.  It registered 39.8 so I placed another thermometer alongside it and the result was the same.  Quite scary.

Wed 20 Jul 2022, 15:11

Also out of the centre of Charlbury, further up the hill and in a shaded area near a running fountain and waterspout but also heated gravel and stones, the maximum yesterday for me was 39.7. But as my thermometer is not of the same professional standard as John Dora's it really does not count.

What I found interesting is that Charlbury was in the Met Office red danger zone, but Witney and Brize Norton were in the orange zone. 

John compares his measurements with those of Brize Norton, but I am not sure how appropriate that is. We are often in  different meteorological areas which, on one very odd occasion, seemed to run through the middle of my house.

John's measurements are usually more aligned with those of Charlbury, rather than Charlbury Youth Hostel, and I usually fit with the latter. This still remains a standard Met Office place by the way, and I do sometimes wonder if they are intercepting the WiFi link between the temperature gauge at the bottom of my garden and the receivers in my house. Or where else are they sampling? 

Wed 20 Jul 2022, 15:08

S'pose Charlbury could be big enough for an urban heat island effect!

Wed 20 Jul 2022, 14:43

John's maximum temperature for yesterday (19th July) was 39.2 C, but that isn't his all time record for Charlbury, which appears back in June 2006, when it hit 39.8 C.

The locality makes quite a difference. A bit further up out of the valley, with a heavily shaded garden with lots of trees the maximum I saw was 37.2 (although I might have missed the absolute maximum). That's fairly close to the Brize Norton official measurement. A more enclosed area with lots of hard surfaces exposed more to the Sun might get significantly more air warming.

A tricky thing this highest temperature business.

Tue 19 Jul 2022, 17:44 (last edited on Tue 19 Jul 2022, 18:06)

I'd, ever since a kid in S. Ontario where weather is really, really, variable what with big shallow freshwater lakes (heat up and cool fast) next to frigid-depthed deep lakes - I've always wanted a weather station of my own! I've now got a 55 foot by 60ft rear garden…

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Tue 19 Jul 2022, 17:20

Thanks Andrew,

Brilliant App, found John's whatsit in a flash.

Tue 19 Jul 2022, 17:19

And try not to post the same thing twice. ;-)

Tue 19 Jul 2022, 16:33

Andrew, cannot recall the exact WMO positioning spec but one standard says to position the instrument a distance equivalent to twice the height of the nearby objects (tree, building etc). 

Tue 19 Jul 2022, 15:28

Peaked here at 34.8 OX7 3LR.  

Tue 19 Jul 2022, 15:25 (last edited on Tue 19 Jul 2022, 15:30)

Thanks John as always for providing the data - I use an app (PWS Monitor) to obsessively check your data every day 😀 - we're currently at a new peak of 38.6…

(Out of interest, John, what's the WMO standard in terms of distance from buildings then?)

Tue 19 Jul 2022, 14:59

My station is a professional weather station (Davis Vantage Pro 2) at WMO standard height but would not be regarded as fully meeting the standard as it's near building (my house). It does seem to show very similar numbers as e.g. Brize Norton so I do regard it as 'accurate'. :) 

Tue 19 Jul 2022, 14:50 (last edited on Tue 19 Jul 2022, 14:54)

Heathrow recorded a provisional 40.2 at 1 p.m. Will probably be beaten later today. 

Tue 19 Jul 2022, 14:45

That'll depend on how accurately John's station is sited wrt reflected heat/shade etc. Heathrow is an official station, you'd need to compare like with like. Brize being the nearest. 

Tue 19 Jul 2022, 14:33

According to John Dora’s weather site just now at 14.25h Charlbury has just beaten the British temperature record of 100.9f or 38.3c. If I recall the temperature of the previous record correctly. What was it? Fry an egg on Heathrow runway? We could try it here on the tennis court. I remember as a child in Southern Ontario when we got the hundred degree days frying eggs on car’s hoods a couple of times. Malcolm using Js account on the tablet